The invention related to magnetic disks and more particularly to such disks which are thin and flexible and are disposed in protective cartridges therefor.
A thin flexible disk rotatably disposed in a protective envelope or cartridge has previously been proposed in U.S. Pat. No. 3,668,658 issued June 6, 1972. The envelope is of vinyl sheet material of considerably greater thickness than the disk, but it is still somewhat flexible; and the envelope closely encloses the disk which is rotatable therein. A porous wipe is disposed between the disk and the inner surfaces of the cartridge so that, as the disk rotates in contact with the wipe, the wipe maintains the surfaces of the disk clean as well as acting as an anti-static agent.
Such an envelope-disk assembly may be used in a disk drive for example of the type disclosed in U.S. Pat. No. 3,846,836, issued Nov. 5, 1974. The disk has a central opening through it and is clamped to be drivingly rotated by means of a tapered collet which moves through the opening of the disk and into a hollow hub so that the disk is clamped between the tapered collet and the hub. Such a tapered collet is not capable of very accurately centering the disk; however, it is sufficiently accurate so that the disk may have 48 magnetic tracks per inch (1.88 tracks per millimeter). The disk is relatively large, being 77/8 inches (200 millimeters) in diameter.